In higher vertebrates, nerve conduction is greatly facilitated by myelin, a lipid-rich membrane that wraps around the axons. Myelin is formed by oligodendrocytes in the central nervous system, and by Schwann cells in the peripheral nervous system. A number of devastating neurodegenerative diseases are known to cause pathological demyelination. .Myelin consists of approximately 70% lipids and 30% proteins and is highly enriched with two glycolipids, galactosylceramide (GalC) and sulfatide (sGalC, 3-sulfate ester of GalC). A unique feature of these myelin glycolipids is that approximately one half of their fatty acyl chains are 2-hydroxy fatty acids. There are no other mammalian tissues that contain such high contents of 2-hydroxy fatty acids, suggesting that the 2- hydroxyl group has a unique role in myelin. Although much is known about the role of GalC and sGalC in myelination, specific function of the 2-hydroxyl group is not well-understood. The long-term goal of this project is to determine the role of the 2-hydroxy fatty acids of GalC and sGalC in myelination and myelin function. Fatty acid 2-hydroxylation is catalyzed by fatty acid 2-hydroxylase, encoded by the Fa2h gene. It is hypothesized that the Fa2h gene product is responsible for the formation of precursors for 2-hydroxy GalC/sGalC biosynthesis, and that incorporation of 2-hydroxy fatty acids into GalC/sGalC is critical for myelination and myelin maintenance. Current evidence show that Fa2h expression, activity, and the lipid products (2-hydroxy fatty acids) increase during the peak myelination period in postnatal mouse brain. In order to test the hypothesis in vivo, a mouse model that lack Fa2h gene will be developed. The mouse Fa2h gene has been cloned, and a targeting vector has been constructed. The targeting vector is designed to delete exon 1 of the gene, which encodes the N-terminal domain required for the fatty acid 2-hydroxylase activity of Fa2h. Fa2h mRNA, 2-hydroxy fatty acids, and fatty acid 2-hydroxylase activities in the brain of Fa2h-knockout mouse will be determined to confirm successful gene targeting. Another targeting vector for conditional knockout will be constructed, which would be used in case of unsuccessful targeting in ES cells, germline-incompetence of targeted ES cell lines, or embryonic lethality of Fa2h-null mutants. The Fa2h-knockout mouse will be used in future studies to determine the role of 2- hydroxy fatty acids of GalC/sGalC in myelination and myelin function. [unreadable] [unreadable] [unreadable]